rosary vs string of beads

rosary and string of beads both are nouns.

Word	Noun	Adjective	Verb	Adverb
rosary	Yes	No	No	No
string of beads	Yes	No	No	No

As nouns, string of beads is a hypernym of rosary; that is, string of beads is a word with a broader meaning than rosary:

rosary: a string of beads used in counting prayers (especially by Catholics)
string of beads: several beads threaded together on a string

Other hypernyms of rosary include beads.

rosary (noun)	string of beads (noun)
a string of beads used in counting prayers (especially by Catholics)	several beads threaded together on a string